This is the 134th most frequent Swedish word.
vad
"What" or "calf" (part of the leg), depending on context.
Here, 'vad' is used as an interrogative pronoun to ask for information about the subject, specifically their name.
Vad heter du?
What is your name?
Here, 'vad' is used as a subordinating conjunction introducing a clause that specifies the nature of the uncertainty.
Jag vet inte vad jag ska göra.
I don't know what I should do.
Here, 'vad' is used exclamatorily to emphasize the extent of appreciation for something, in this case, a car.